Summary

Phage therapy is the use of bacteriophages—viruses that infect and replicate within a bacterium—to treat pathogenic bacteria. This approach had a short history in the premolecular era of Western medicine, but it died out before the mid-20th century mainly as a result of justly critical reports from the American Medical Association and the development of chemical antibiotics (1). Now, the global antibiotic resistance crisis and a new appreciation for the importance of the human microbiota have led to a resurgence of interest in phage therapy, not only in the classic sense of treating bacterial infections (2) but also for its potential role in modulating microbiota (3). A landmark 2015 meeting (4) on phage-based therapeutics hosted by the U.S. National Institute of Allergy and Infectious Diseases (NIAID) included not only phage biologists but also participants from private companies, public and governmental research organizations, clinicians, and the federal regulatory community. Opinions on the practicality of phage applications replacing traditional antibiotic regimens ranged from full-speed ahead, mostly from the biotechnology industry, to overt skepticism on the part of some physicians. In any case, participants left the meeting convinced that a “Phage Therapy 2.0” is on its way.